Cutting tip adjusting device

Description

[0001] The present invention is related to a machine tool of the type having a rotatably mounted spindle shaft having a longitudinal axis of rotation and adapted for having coupled thereto a tool holder having a plurality of cutting inserts which are adjustable radially of the axis before, during, or after the cutting operation depending on the work being done.

Description Of The Prior Art

[0002] Presently, parts can be machined to very close tolerances and at high speeds often without the need for secondary operations such as honing, grinding and lapping.

[0003] Great improvements have been made in machine tools, particularly those tools which provide automatic adjustment for cutting tool inserts radially inward or outward, as and when desired, to, for example, compensate for wear of the cutting edge, for boring, turning, grooving, finishing on a retract stroke, to withdraw the tool from a workpiece without marking the side wall of a finished bore, or for bore sizing and contour boring. One cutting machine which has provided significant advances in achieving these results is described in US-A. 3,740,161. With this tool, the cutting edges of all of the inserts can be automatically adjusted outwardly and inwardly precisely and quickly without human intervention and possible error, and downtime. However, the hydraulic mechanism used has caused alignment concerns which have limited the use of such equipment to its fullest advantage. Alignment concerns have been particularly difficult at high speeds.

[0004] Another problem results from the fact that often state of the art cutting machines do not include hydraulic systems. With such machinery it is necessary to modify the basic cutting machine by supplementing it with an auxiliary hydraulic system. In addition to the fact that such an addition must be provided for, problems associated with the use of hydraulic apparatus are incurred. For example, hydraulic systems include various hydraulic pumps which tend to be noisy and also require attention in order to be maintained in acceptable operating condition. In addition, other hardware associated with a hydraulic system is required which adds to the cost and upkeep of such apparatus. In addition, it is not uncommon for hydraulic systems to operate continuously throughout the day even though the particular machine with which the system is associated may not be in use. Such continuous use obviously involves an unnecessary use of energy. In addition, various components of a hydraulic cutting machine may have a reduced life due to repetitive operation caused by continual stroking of the hydraulic mechanism.

[0005] The addition of a hydraulic system also will require the addition of a control system to control the hydraulic equipment. Thus two systems will be required; one to control the cutting tool per se and one to control the hydraulic apparatus.

[0006] A further concern is that the actual control of the orientation or location of the cutting tool tends to be rather complicated when a hydraulic system is being used.

[0007] A related problem is that the known prior art machine tools are not as compact as desired in the sense that the entire mechanism which causes radial movement of the inserts is not mounted directly to the spindle shaft of the tool, and this tends to aggravate the alignment concern.

[0008] An example of such a machine tool is known from DE-A-1 920 939 describing the closest prior art in which the compensator mechanism is not integral with the spindle. Hence, the spindle and the compensator are resting upon the machine table, one after the other. It is necessary that the compensator is aligned precisely with the spindle both vertically and horizontally to avoid damage to the bearings. If the spindle and compensator are spaced as shown in DE-A-1 920 939, there would ordinarily be realignment of the spindle to the workpiece without also realignment of the compensator. This will cause the drawbar to bend which in turn causes a bending moment on the bearings. Further, the compensator is not mounted to a spindle shaft but the rod extends between the spindle and the compensator. Such a structure will cause the thrust force to unload the bearings at high speed operation and such unloading causes premature failure of the bearings.

[0009] In the present invention the above problems are overcome by the fact that a roller screw mechanism for actuation of a drawbar for the operation of cutting elements of the machine tool is mounted within an opening of the rotatable spindle shaft, said spindle shaft being journalled by the aid of a plurality of ball bearings for rotation in relation to a non-rotatable spindle body, and by the fact that a stationary motor mount is journalled within a motor mount housing, said housing being rotatably connected to the stationary motor mount being arranged to turn a leadscrew spindle included in the roller screw mechanism for actuation of the drawbar.

[0010] It is highly desirable to provide a machine tool which can be operated without concern about tool alignment considerations. It is also desirable to solve this problem and at the same time eliminate the need for an auxiliary system, particularly an auxiliary hydraulic system with all of the problems noted herein associated with such a system. It is also desirable to provide a machine tool wherein what is referred to in the art as a closed loop system may be utilized. In such a system, means are provided for orienting or locating the cutting tool in such a manner that simultaneously with such tool orientation signals are sent back to the orientation means to identify the cutting tool location and thereby facilitate proper positioning of the tool.

Summary Of The Invention

[0011] This invention achieves these and other results by providing an adjustable tool drive assembly of the type surrounding a longitudinal axis of rotation and adapted for having coupled thereto a tool holder which rotates about said axis and includes at least one cutting tool which is adjustable radially of said axis, said adjustable tool drive assembly comprising
a spindle casing for non-rotatable mounting having a cavity therein extending along said axis from a first end to a second end;
a spindle shaft rotatably mounted in said spindle casing extending through said cavity, having an opening therethrough extending along said axis from one end to the other, said one end adapted to be coupled to said tool holder;
   the rotatable spindle shaft being journalled by means of a plurality of ball races at least at the ends of the shaft for rotation in relation to said non-rotatable spindle casing;
means coupled to said rotatable spindle shaft for rotating said rotatable spindle shaft;
a roller screw including a leadscrew spindle extending along said axis and at least one nut body operatively coupled thereto, said roller screw being so mounted that rotary motion of said leadscrew spindle about said axis causes movement of said at least one nut body along said axis relative to the spindle shaft;
means including a drive shaft coupled from said leadscrew spindle to the motor for controllably rotating said leadscrew spindle;
means including a drawbar which is reciprocally mounted within said opening and extends along said axis, said drawbar being adapted to be coupled to said tool
holder for rotation therewith when said tool holder is rotated and for causing radial movement of said cutting tool when said drawbar is reciprocated; and
means positioned within said opening and coupled to said drawbar and to said at least one nut body for reciprocating said drawbar along said axis in response to movement of said at least one nut body along said axis, said reciprocating means being non-rotatable
characterized by the fact that the roller screw including the leadscrew spindle and the at least one nut body is mounted within said opening of the rotatable spindle shaft, and that a motor mount housing is journalled upon a stationary motor mount, the housing being rotatably connected to the rotatable spindle shaft, the motor mounted to the stationary motor mount being arranged to turn the leadscrew spindle for actuation of the drawbar.
The above mentioned results are also achieved by providing an adjustable tool drive assembly of the type surrounding a longitudinal axis of rotation and adapted for having coupled thereto a tool holder which rotates about said axis and includes at least one cutting tool which is adjustable radially of said axis, said adjustable tool drive assembly comprising
a spindle shaft rotatably mounted and having an axis and having a first and second end, said first end adapted to be coupled to said tool holder;
means coupled to said second end of said rotatable spindle shaft for rotating said rotatable spindle shaft, said rotating means including a housing extending away from said second end and having an opening therethrough extending along said axis from one end of said housing to the other;
a roller screw including a leadscrew spindle extending along said axis and at least one nut body operatively coupled thereto, said roller screw being so mounted that rotary motion of said leadscrew spindle about said axis causes movement of said at least one nut body along said axis;
means including a coupling coupled from said leadscrew spindle to the motor shaft of the motor for controllably rotating said leadscrew spindle;
means including a drawbar which is reciprocatably mounted within said rotatable spindle shaft and extends along said axis, said drawbar being adapted to be coupled to said tool holder for rotation therewith when said tool holder is rotated and for causing radial movement of said cutting tool when said drawbar is reciprocated; and
means positioned within said opening and coupled to said drawbar and to said at least one nut body for reciprocating said drawbar along said axis in response to movement of said at least one nut body along said axis,
characterized by the fact that the roller screw including the leadscrew spindle and the at least one nut body is mounted within said opening of said housing, that said housing by the aid of ball races at least at the ends of the housing is journalled for rotation around a stationary sleeve housing the roller screw, and that a stationary motor mount for the motor arranged to turn the leadscrew spindle for actuation of the drawbar, is fixed to the stationary sleeve.

Brief Description of the Drawings

[0012] The objects, features and advantages of the present invention will be clearly understood to those skilled in the art by reference to this disclosure and the attached drawings in which:

Figure 1 is a cross sectional view of one embodiment of the present invention;

Figure 2 is a cross sectional view of another embodiment of the present invention; and

Figure 3 is a view of one embodiment of a cutting machine incorporating the machine tool of the present invention.

Description Of The Preferred Embodiments

[0013] The embodiment of this invention which is illustrated in Figure 1 is particularly suited for achieving the objects of this invention. Figure 1 depicts a machine tool 2 of the type having a rotatably mounted housing 4 circumscribing a longitudinal axis of rotation 6 and adapted for having coupled thereto in a known manner a tool holder 8. Tool holder 8 includes at least one cutting tool which is adjustable radially of the axis 6. Cutting tools are depicted in Figure 1 in the form of tool inserts 10 and 12 each of which has a cutting edge which is caused to engage and disengage a workpiece in a known manner to cut the workpiece during rotation of the housing 4 about axis 6.

[0014] A drawbar 14 extends along axis 6 and is reciprocatably mounted within housing 4 and adapted for coupling in a known manner to the tool holder 8 for causing the radial movement of the cutting tool in response to reciprocation of the drawbar. For example, in the apparatus of Figure 1, drawbar 14 is coupled to the drawbar extension 16 of tool holder 8. Reciprocation of drawbar 14 causes corresponding reciprocation of drawbar extension 16 causing the cutting inserts 10 and 12 to pivot in a radial direction relative to axis 6 as a result of a camming action between camming surfaces 18 and 20 of drawbar extension 16 and cam followers 22 and 24 of cutting inserts 10 and 12, respectively.

[0015] Means are provided for coupling housing 4 and drawbar 14 for rotating the drawbar about axis 6 when housing 4 rotates about axis 6, without preventing the reciprocation of the drawbar within the housing. For example, tool holder 8 is bolted to housing 4 at interface 26. Drawbar extension 16 is threaded to drawbar 14 at interface 28 and is keyed to the tool holder for rotation therewith by means of a keyway 32 which slides relative to key member 30 fixed to tool holder 8.

[0016] The housing 4 of machine tool 2 is depicted in Figure 1 as including a spindle shaft 34 which is rotatably mounted in a known manner within a spindle casing 36. Rotation of the spindle shaft 34 relative to spindle casing 36 and about axis 6 is facilitated by a plurality of ball races 38. Although races 38 are only depicted at the left hand end of the spindle shaft 34 as viewed in Figure 1, it will be understood that other ball races 38, not shown, will also be positioned at least at the right hand end of the spindle shaft 34.

[0017] The spindle shaft 34 has attached to one end thereof means for rotating the shaft discussed in more detail hereinafter.

[0018] Means are coupled to housing 4 for rotating the housing about axis 6. For example, spindle shaft 34 can have means such as a pulley 40 attached to one end thereof by a pulley locknut 42. In addition, a pulley key 44 extends into a keyway 46 to facilitate rotation of the spindle shaft 34. In operation, the spindle shaft is caused to rotate by pulley 40 and drive belt 48 in a known manner.

[0019] A roller screw 50 is also mounted within the housing 4. Roller screw 50 includes a leadscrew spindle 52 extending along axis 6. Also provided is at least one nut body operatively coupled to the leadscrew spindle. In Figure 1, nut bodies 54 and 56 are operatively coupled to the leadscrew spindle 52. The roller screw 50 is mounted within housing 4 such that rotary motion of the leadscrew spindle 52 about axis 6 causes movement of the nut bodies 54 and 56 along axis 6.

[0020] Means within the housing 4 is coupled to the drawbar 14 and nut bodies 54 and 56 for reciprocating the drawbar along axis 6 in response to movement of the nut bodies 54 and 56 along axis 6. For example, Figure 1 depicts a slide member 58 extending along axis 6 and having a first open end 60 and an axially spaced second open end 62. One end 64 of drawbar 14 extends into the first open end 60 and includes means coupled thereto for preventing axial movement of the drawbar relative to the slide member but permiting the drawbar to rotate relative to the slide member. For example, drawbar 14 is mounted for rotation within slide member 58 by means of ball bearings 66 which are held in place by a clamping ring 68 bolted (not shown) to the slide member and by a bearing locknut 70, as well as by opposing shoulders of the slide member and the drawbar.

[0021] A portion 72 of the leadscrew spindle 52 extends into the second open end 62 of the slide member 58. A spacer serves to separate and preload the nut bodies, In particular, and as depicted in Figure 1 of the drawings, nut bodies 54 and 56 are separated by a spacer and operatively coupled to portion 72 of the leadscrew spindle, as for example, by inner and outer threads of the nut bodies and leadscrew spindle, respectively. Nut bodies 54 and 56 are held in place by a locknut, attachment of the slide member 58 being further facilitated by screws (not shown). In this manner, movement of the nut bodies relative to the slide member is prevented.

[0022] Means are coupled to leadscrew spindle 52 for rotating the leadscrew spindle about axis 6. For example, Figure 1 depicts a motor 74. Means are provided for coupling a portion 76 of the leadscrew spindle extending out of the second open end 62 of the slide member 58 to the motor 74. For example, a drive shaft 78 extends within the spindle shaft 34. One end 80 of the drive shaft 78 is coupled to the motor 74 by means of a coupling 82 having pins 84 and 86 extending therethrough and through the shaft 78 and motor shaft 88, respectively, in a known manner as shown in the drawing. The other end 90 of the drive shaft 78 is coupled to the leadscrew spindle 52 by means of a pin 92 extending through the leadscrew spindle, one end of which extends into a recess or bore in shaft 78, and through the shaft 78, in a known manner as shown in the drawing.

[0023] In order to facilitate rotation of the drive shaft 78, a stationary sleeve 94 is positioned within the spindle shaft 34. Drive shaft 78 extends through the sleeve opening or bore 96 which extends from one sleeve end to an opposing sleeve end. In order to prevent rotation of the slide member 58 within the spindle shaft 34, slide member 58 is keyed to the stationary sleeve 94 by means of a key 98 which slides in a keyway 100 of sleeve 94. Portion 76 of leadscrew spindle 52 is mounted for rotation relative to the sleeve 94 by ball bearings depicted as being held in place between a first locknot and shoulder of sleeve 94 and a second locknut and shoulder of spindle 52.

[0024] Figure 1 depicts a motor mount housing 102 coupled to pulley 40 by means of four bolts 104. A stationary motor mount 106 is coupled to the housing 102. In particular, a clamp ring 108 engages one shoulder of housing 102 and positions the rotating portion of bearings 110 and 112, separated by spacer 116, against another shoulder of housing 102. In a like manner the stationary portion of bearings 110 and 112 are spaced by spacer 114 and urged against a shoulder of the motor mount 106 by a locknut 118 depicted threaded to the left end of the motor mount. Motor 74 is bolted to the stationary motor mount 106 as depicted in the drawing.

[0025] In the alternative embodiment of Figure 2 the roller screw apparatus is positioned external of the spindle shaft. In this embodiment, the machine tool 200 includes a rotatably mounted housing including the spindle shaft 202 and the body portion 204 both of which are coupled to the pulley 206. For example, spindle shaft 202 is coupled to pulley 206 by a pulley locknut 208 and is keyed to the pulley to facilitate mutual rotation of the pulley and the spindle shaft by key 210 and keyway 212. On the other hand, body portion 204 is attached to pulley 206 by means of bolts 214, only one of which is shown. The rotatably mounted housing includes the spindle shaft 202 and body portion 204 and is generally identified by reference numeral 216. Housing 216 is caused to rotate about axis 218 by pulley 206 and a drive belt in a known manner.

[0026] A drawbar 220 extends along axis 218 and is reciprocatably mounted within the housing 216. Although not shown in Figure 2, drawbar 220 extends to the left beyond Figure 2, through spindle shaft 202 which is mounted in a known manner within a spindle body (not shown) similar to spindle body 36 of Figure 1, for coupling to a tool holder such as tool holder 8 of Figure 1 for causing the radial movement of the cutting tool 10 and 12 in response to reciprocation of the drawbar as described herein.

[0027] A roller screw 222 is mounted within body portion 204 of housing 216. Roller screw 222 includes a leadscrew spindle 224 extending along axis 218. Also provided are nut bodies 226 and 228 which are operatively coupled to the leadscrew spindle 224. The roller screw 222 is mounted within body portion 204 such that rotary motion of the leadscrew spindle about axis 218 causes movement of the nut bodies 226 and 228 along axis 218.

[0028] A slide member 230 extends along axis 218 and includes a first open end 232 and an axially spaced second open end 234. One end 236 of the drawbar 220 extends into the open end 232 and includes means coupled thereto for preventing axial movement of the drawbar relative to the slide member but permitting the drawbar to rotate relative to the slide member. For example, drawbar 220 is mounted for rotation within slide member 230 by means of ball bearings 238 which are held in place by locknuts 240 and 242 and an opposing shoulder of the slide member, and by a bearing locknut 244 and an opposing shoulder of the drawbar. Slide member 230 provides means for reciprocating the drawbar 220 along axis 218 in response to movement of the nut bodies 226 and 228 along axis 218.

[0029] A portion 246 of the leadscrew spindle 224 extends into the second open end 234 of the slide member 230. A spacer serves to separate and preload the nut bodies. As depicted in Figure 2 of the drawings, nut bodies 226 and 228 are separated by a spacer and operatively coupled to portion 246 of the leadscrew spindle, as for example, by inner and outer threads of the nut bodies and leadscrew spindle, respectively. Nut bodies 226 and 228 are held in place by a clamp ring and screws, attachment to the slide member 230 being further facilitated by screws 248. In this manner, movement of the nut-bodies relative to the slide member is prevented. Portion 246 extends into a bore in an adjacent end of drawbar 220. Clearance is provided between the leadscrew spindle and the bore surface so that the drawbar does not rotate with the spindle, and is free to reciprocate relative to the spindle, during spindle rotation.

[0030] Means are coupled to the leadscrew spindle for rotation thereof about axis 218. For example, Figure 2 depicts a motor 250. Means are provided for coupling a portion 252 of the leadscrew spindle extending out of the second open end 234 of the slide member 230 to the motor 250. As shown in Figure 2, a coupling 254 is attached to motor shaft 256 by pin 258 and to portion 252 of the leadscrew spindle by set screw 260.

[0031] In order to facilitate reciprocation of slide member 230 along axis 218 a stationary sleeve 262 is provided. Slide member 230 slides in the bore 264 of sleeve 262 and is guided by means of a roll pin 266 extending from the slide member 230 to a guideway 268 in the sleeve 262.

[0032] Figure 2 depicts a stationary motor mount 270 coupled to the sleeve 262 by bolts 272 only one of which is shown. Rotation of the leadscrew spindle relative to the motor mount 270 is facilitated by ball bearings 274 held in place by flanged portions of the motor mount and leadscrew spindle and by ring 276 and locknut 278.

[0033] Rotation of the body portion 204 of the rotatably mounted housing 216 relative to the stationary motor mount 270 is facilitated by the stationary portion of races 280 and 282 spaced by a spacer 284 and held in place by a flanged end of the sleeve 262 and locknut 286, and also spaced by a spacer 288 and held in place by a flanged end of the body portion 204 and a clamped ring 290 with bolts. Possible rotation of the motor 250 and a motor mount 270 caused by bearing friction can be prevented by bracketing the motor and mount in place.

[0034] The embodiments of Figure 1 and 2 operate essentially in the same manner. For example, and referring to Figure 1, the drive shaft 78 is caused to rotate by motor 74. Rotation of the drive shaft causes the leadscrew spindle 52 to rotate. Such rotation of the leadscrew spindle causes the nut bodies 54 and 56 which are threaded upon spindle 52 to move relative thereto in an axial direction along axis 6. Since the nut bodies 54 and 56 are coupled to the slide member 58, movement of the nut bodies causes corresponding movement of the slide member along axis 6. Since the slide member 58 is coupled to the drawbar 14 such movement of the slide member causes corresponding movement of the drawbar along the axis 6 thereby causing the cutting inserts 10 and 12 to pivot in a radial direction relative to axis 6 as a result of a camming action between camming surfaces 18 and 20 of drawbar extension 16, to which drawbar 14 is coupled, and cam followers 22 and 24 of cutting inserts 10 and 12, respectively. By controlling the speed and rotational direction of motor shaft 88, cutting tools 10 and 12 can be caused to pivot towards and away from a workpiece as quickly as and to the extent desired.

[0035] The actual cutting operation results from rotation of the spindle shaft 34 and the tool holder 8 attached thereto to which the cutting tools 10 and 12 are coupled. Rotation of the spindle shaft is caused by the rotation of pulley 40 by drive belt 48 in a known manner.

[0036] The embodiment of Figure 2 operates in essentially the same manner with the exception that the motor shaft 256 is coupled directly to the leadscrew spindle 224.

[0037] Regarding Figures 1 and 2, the various ball bearings referred to herein and depicted in the drawings include bearings known in the art to comprise an inner and outer race having a ball or roller therebetween. In such bearings the ball, and race adjacent the moving part, rotate during operation of the apparatus. The use of such bearings is by way of example only.

[0038] In the apparatus of Figures 1 and 2 the motor 74, 250 preferably comprises a stepper motor drive apparatus of the type described in US-A 4,223,260. In a like manner, a controller of the type described in US-A 4,268,783 can be used. However, the use of such a stepper motor and controller is by way of example only.

[0039] An example of a cutting machine incorporating the machine tool of the present invention is depicted in Figure 3. Figure 3 depicts a cutting machine 300 generally of the type described in US-A 3,740,161 but substituting a machine tool such as machine tool 2 which is of the type described herein and depicted in Figure 1. The machine tool 2 includes a tool holder 8 having tool inserts 10 and 12 (not shown). The tool holder 8 is attached to the rotatably mounted housing 4 which is shown as extending from one end of the cutting apparatus 302. The motor 74 extends from the other end of the cutting apparatus 302. The pulley 40 and belt 48 are housed in a housing 304, the pulley being driven by a motor 306 in a known manner. The cutting machine 300 is described in detail in US-A 3,740,161 and reference is made thereto for a description of the general operation of such a machine. However, it is to be noted that the entire cutting apparatus 302 is caused to slide along rails 308 and 310 so that the tool holder 8 is positioned for engagement of the workpiece 312 by the tool inserts 10 and 12 as already described in detail herein.

[0040] Although in the examples described herein the roller screw includes at least one nut body operatively coupled to the leadscrew spindle by inner and outer threads of the nut body and leadscrew spindle, respectively, such structure is by way of example only. Roller screws are well known in the art, and any type of roller screw which translates rotary motion into reciprocating motion may be engineered for use with the present invention. Examples, without limitation, include roller screws of the type sold under the trademark ROLLSCREW®

[0041] The machine tool of the present invention can be used in a closed loop system if desired. For example, in the apparatus of Figure 1, motor 74 represents a stepper motor coupled to an encoder 120. The motor and encoder are shown schematically as being coupled to a controller 122, as, for example, a controller of the type disclosed in US-A 4,268,783. Such combined structure is useful in assuring predetermined precision radial movement of cutting inserts as described herein. The use of an encoder in cutting applications is known in the art and will not be discussed further.

[0042] The embodiments which have been described herein are but some of several which utilize this invention and are set forth here by way of illustration but not of limitation. It is apparent that many other embodiments which will be readily apparent to those skilled in the art may be made without departing materially from the spirit and scope of this invention as claimed.

Claims

1. An adjustable tool drive assembly (2) of the type surrounding a longitudinal axis of rotation (6) and adapted for having coupled thereto a tool holder (8) which rotates about said axis (6) and includes at least one cutting tool (10, 12) which is adjustable radially of said axis (6), said adjustable tool drive assembly (2) comprising
a spindle casing (36) for non-rotatable mounting having a cavity therein extending along said axis (6) from a first end to a second end;
a spindle shaft (34) rotatably mounted in said spindle casing extending through said cavity, having an opening therethrough extending along said axis (6) from one end to the other, said one end adapted to be coupled to said tool holder (8);
   the rotatable spindle shaft (34) being journalled by means of a plurality of ball races (38) at least at the ends of the shaft (34) for rotation in relation to said non-rotatable spindle casing (36) ;
means coupled to said rotatable spindle shaft (34) for rotating said rotatable spindle shaft (34);
a roller screw (50) including a leadscrew spindle (52) extending along said axis (6) and at least one nut body (54, 56) operatively coupled thereto, said roller screw (50) being so mounted that rotary motion of said leadscrew spindle (52) about said axis (6) causes movement of said at least one nut body (54, 56) along said axis (6) relative to the spindle shaft;
means including a drive shaft (78) coupled from said leadscrew spindle (52) to the motor (74) for controllably rotating said leadscrew spindle (52).
means including a drawbar (14) which is reciprocally mounted within said opening and extends along said axis (6), said drawbar being adapted to be coupled to said tool holder (8) for rotation therewith when said tool holder (8) is rotated and for causing radial movement of said cutting tool (10, 12) when said drawbar (14) is reciprocated; and
means positioned within said opening and coupled to said drawbar (14) and to said at least one nut body (54, 56) for reciprocating said drawbar (14) along said axis (6) in response to movement of said at least one nut body (54, 56) along said axis (6), said reciprocating means being non-rotatable
characterized by the fact that the roller screw (50) including the leadscrew spindle (52) and the at least one nut body (54, 56) is mounted within said opening of the rotatable spindle shaft (34), and that a motor mount housing (102) is journalled upon a stationary motor mount (106), the housing (102) being rotatably connected to the rotatable spindle shaft (34), the motor (74) mounted to the stationary motor mount (106) being arranged to turn the leadscrew spindle (52) for actuation of the drawbar (14).

2. The tool of claim 1 wherein said reciprocating means includes a slide member (58) extending along said axis (6) and having a first open end (60) and an axially spaced second open end (62) and wherein one end of said drawbar (14) extends into said first open end (60) and includes means coupled thereto for preventing axial movement of said drawbar (14) relative to said slide member (58) but permitting said drawbar (14) to rotate relative to said slide member (58).

3. The tool of claim 2 wherein a portion (72) of said leadscrew spindle (52) extends into said second open end (62) of said slide member (58), and said at least one nut body (54, 56) is operatively coupled to said portion (72) and attached to said slide member (58) to prevent movement of said at least one nut body (54, 56) relative to said slide member (58).

4. The tool of claim 2 wherein said leadscrew spindle (52) rotating means is a motor (74), and further including means for coupling a portion (76) of said leadscrew spindle (52) extending out of said second open end (62) of said slide member (58) to said motor (74).

5. The tool of claim 4 wherein said coupling means includes a drive shaft (78) which extends within said spindle shaft (34), one end (80) of said drive shaft (78) being coupled to said motor (74) and the other end (90) of said drive shaft (78) being coupled to said leadscrew spindle (52).

6. The tool of claim 5 further including a stationary sleeve (94) positioned within said spindle shaft (34) and keyed to said slide member (58), and wherein said drive shaft (78) extends through said sleeve (94) by means of an opening (96) extending from one sleeve end to an opposing sleeve end.

7. The tool of claim 4 wherein said motor (74) is a stepper motor.

8. The machine tool of claim 7 wherein said motor (74) is coupled to a controller mechanism.

9. The tool of claim 1 including a tool holder (8) which is coupled to said one end of said rotatable spindle shaft (34) and which is coupled to said drawbar (14), said tool holder (8) having coupled thereto a cutting tool (10, 12) for cutting a workpiece during rotation of said rotatable spindle shaft (34) about said axis (6), said cutting tool (10, 12) being caused to move in a radial direction relative to said axis (6) such that a cutting edge of said cutting tool (10, 12) is caused to engage and disengage a workpiece as a result of a camming action between said cutting tool (10, 12) and said drawbar (14) as said drawbar is caused to reciprocate along said axis (6).

10. The tool of claim 9 wherein said leadscrew spindle (52) rotating means is a motor (74).

11. The tool of claim 10 wherein said motor (74) is a stepper motor.

12. The tool of claim 8 wherein an encoder is coupled to said controller mechanism and said motor (74).

13. The tool of claim 11 wherein said motor (74) is coupled to a controller mechanism.

14. The tool of claim 13 wherein an encoder is coupled to said controller mechanism and said motor (74).

15. An adjustable tool drive assembly (200) of the type surrounding a longitudinal axis of rotation (218) and adapted for having coupled thereto a tool holder which rotates about said axis (218) and includes at least one cutting tool which is adjustable radially of said axis (218), said adjustable tool drive assembly (200) comprising
a spindle shaft (202) rotatably mounted and having an axis (218) and having an axis (218) and having a first and second end, said first end adapted to be coupled to said tool holder;
means coupled to said second end of said rotatable spindle shaft (202) for rotating said rotatable spindle shaft (202), said rotating means including a housing (216) extending away from said second end and having an opening therethrough extending along said axis (218) from one end of said housing (216) to the other;
a roller screw (222) including a leadscrew spindle (224) extending along said axis (218) and at least one nut body (226, 228) operatively coupled thereto, said roller screw (222) being so mounted that rotary motion of said leadscrew spindle (224) about said axis (218) causes movement of said at least one nut body (226, 228) along said axis (218);
means including a coupling (254) coupled from said leadscrew spindle (224) to the motor shaft (256) of the motor (250) for controllably rotating said leadscrew spindle (224),
means including a drawbar (220) which is reciprocally mounted within said rotatable spindle shaft (202) and extends along said axis (218), said drawbar (220) being adapted to be coupled to said tool holder for rotation therewith when said tool holder is rotated and for causing radial movement of said cutting tool when said drawbar (220) is reciprocated; and
means positioned within said opening and coupled to said drawbar (220) and to said at least one nut body (226, 228) for reciprocating said drawbar (220) along said axis (218) in response to movement of said at least one nut body (226, 228) along said axis (218),
characterized by the fact that the roller screw (222) including the leadscrew spindle (224) and the at least one nut body (226, 228) is mounted within said opening of said housing (216), that said housing (216) by the aid of ball races (280, 282) at least at the ends of the housing (216) is journalled for rotation around a stationary sleeve (262) housing the roller screw (222), and that a stationary motor mount (270) for the motor (250) arranged to turn the leadscrew spindle (224) for actuation of the drawbar (220), is fixed to the stationary sleeve (262).

Revendications

1. Ensemble ajustable (2) d'entraînement d'outil du type entourant un axe longitudinal de rotation (6) et adapté pour être accouplé à un porte-outil (8) qui tourne autour dudit axe (6) et comprend au moins un outil de coupe (10,12), qui est ajustable radialement par rapport audit axe (6), ledit ensemble ajustable (2) d'entraînement d'outil comprenant
un carter de broche (36) permettant un montage non rotatif et contenant une cavité s'étendant le long dudit axe (6) depuis une première extrémité jusqu'à une seconde extrémité;
un arbre de broche (34) monté rotatif dans ledit carter de broche, traversant ladite cavité et possédant une ouverture s'étendant le long dudit axe (6), d'une extrémité à l'autre, ladite première extrémité étant adaptée à être accouplée audit porte-outil (8);
l'arbre rotatif de broche (34) étant tourillonné au moyen d'une pluralité de chemins de roulement de billes (38) situés au moins aux extrémités de l'arbre (34) de manière à tourner par rapport audit carter de broche non rotatif (36);
des moyens accouplés audit arbre rotatif de broche (34) pour faire tourner cet arbre;
une vis à rouleaux (50) comprenant une broche filetée (52) s'étendant le long dudit axe (6) et au moins un corps formant écrou (54,56) qui lui est accouplé de façon opérationnelle, ladite vis à rouleaux (50) étant montée de telle sorte qu'un mouvement de rotation de ladite broche filetée (52) autour dudit axe (6) provoque le déplacement dudit au moins un corps formant écrou (54,56) le long dudit axe (6) par rapport à l'arbre de broche;
des moyens incluant un arbre d'entraînement (78) accouplé entre ladite broche filetée (50) et le moteur (74) pour entraîner en rotation, d'une manière commandable, ladite broche filetée (52);
des moyens comprenant une barre de traction (14) qui est montée, de manière à être déplaçable en va-et-vient, dans ladite ouverture et s'étend le long dudit axe (6), ladite barre de traction étant adaptée pour être accouplée audit porte-outil (8) pour tourner de concert avec ce dernier lorsque ledit porte-outil (8) tourne, et pour provoquer un déplacement radial dudit outil de coupe (10,12) lorsque ladite barre de traction (14) est déplacée en va-et-vient; et des moyens positionnés dans ladite ouverture et accouplés à ladite barre de traction (14) et audit au moins un corps formant écrou (54,56) pour déplacer en va-et-vient ladite barre de traction (14) le long dudit axe (6) en réponse au déplacement dudit au moins un corps formant écrou (54,56) le long dudit axe (6), lesdits moyens à déplacement en va-et-vient ne pouvant pas tourner;
caractérisé en ce que la vis à rouleaux (50), qui comprend la broche filetée (52) et le au moins un corps formant écrou (54,56), est montée dans ladite ouverture de l'arbre de broche rotatif (34), et qu'un logement (102) du support du moteur est tourillonné sur un support fixe (106) du moteur, le logement (102) étant raccordé, de manière à pouvoir tourner, à l'arbre rotatif (34) de la broche, le moteur (74) monté sur le support fixe (106) du moteur étant agencé de manière à faire tourner la broche filetée (52) pour actionner la barre de traction (14).

2. Outil selon la revendication 1, dans lequel lesdits moyens à déplacement en va-et-vient comprennent un coulisseau (58) s'étendant le long dudit axe (6) et possédant une première extrémité ouverte (60) et une seconde extrémité ouverte distante axialement (62), et dans lequel une extrémité de ladite barre de traction (14) pénètre dans ladite première extrémité ouverte (60) et comprend des moyens accouplés à cette extrémité pour empêcher un déplacement axial de ladite barre de traction (14) par rapport audit coulisseau (58), mais permettant à ladite barre de traction (14) de tourner par rapport audit coulisseau (58).

3. Outil selon la revendication 2, dans lequel une partie (72) de ladite broche filetée (52) pénètre dans ladite seconde ouverture (62) dudit coulisseau (58), et ledit au moins un corps formant écrou (54,56) est accouplé de façon opérationnelle à ladite partie (72) et est raccordé audit coulisseau (58) de manière à empêcher un déplacement dudit au moins un corps formant écrou (54,56) par rapport audit coulisseau (58).

4. Outil selon la revendication 2, dans lequel lesdits moyens d'entraînement en rotation de la broche filetée (52) sont constitués par un moteur (74), et dans lequel il est en outre prévu des moyens pour accoupler une partie (76) de ladite broche filetée (52), qui s'étend à l'extérieur de ladite seconde extrémité ouverte (62) dudit coulisseau (58), audit moteur (74).

5. Outil selon la revendication 4, dans lequel lesdits moyens de couplage comprennent un arbre d'entraînement (78) qui s'étend à l'intérieur dudit arbre de broche (34), une extrémité (80) dudit arbre d'entraînement (78) étant accouplée audit moteur (74), et l'autre extrémité (90) dudit arbre d'entraînement (78) étant accouplé à ladite broche filetée (52).

6. Outil selon la revendication 5, comprenant en outre un manchon fixe (94) disposé à l'intérieur dudit arbre de broche (34) et claveté sur ledit coulisseau (58), et dans lequel ledit arbre d'entraînement (78) traverse ledit manchon (94) au niveau d'une ouverture (96) s'étendant depuis une extrémité du manchon jusqu'à une extrémité opposée de ce dernier.

7. Outil selon la revendication 4, dans lequel ledit moteur (74) est un moteur pas-à-pas.

8. Outil selon la revendication 7, dans lequel ledit moteur (74) est accouplé à un mécanisme de commande.

9. Outil selon la revendication 1 comprenant un porte-outil (8) qui est accouplé à ladite une extrémité dudit arbre de broche rotatif (34) et qui est accouplé à ladite barre de traction (14), ledit porte-outil (8) étant accouplé à un outil de coupe (10,12) servant à découper une pièce à usiner pendant la rotation dudit arbre rotatif de broche (34) autour dudit axe (6), ledit outil de coupe (10,12) étant amené à se déplacer dans une direction radiale par rapport audit axe (6) de sorte qu'un bord de coupe dudit outil de coupe (10,12) est amené à s'appliquer contre et à se dégager d'une pièce à usiner en tant que résultat d'une action de came entre ledit outil de coupe (10,12) et ladite barre de traction (14) lorsque cette dernière est amenée à se déplacer en va-et-vient le long dudit axe (6).

10. Outil selon la revendication 9, dans lequel lesdits moyens d'entraînement en rotation de la broche filetée (52) sont constitués par un moteur (74).

11. Outil selon la revendication 10, dans lequel ledit moteur (74) est un moteur pas-à-pas.

12. Outil selon la revendication 8, dans lequel un codeur est accouplé audit mécanisme de commande et audit moteur (74).

13. Outil selon la revendication 11, dans lequel ledit moteur (74) est accouplé à un mécanisme de commande.

14. Outil selon la revendication 13, dans lequel un codeur est accouplé audit mécanisme de commande et audit moteur (74).

15. Ensemble ajustable (200) d'entraînement d'outil du type entourant un axe longitudinal de rotation (218) et adapté pour être accouplé à un porte-outil qui tourne autour dudit axe (218) et comprend au moins un outil de coupe qui est ajustable radialement par rapport audit axe (218), ledit ensemble ajustable (200) d'entraînement d'outil comprenant
un arbre de broche (202) monté de manière à pouvoir tourner et possédant un axe (218) et des première et seconde extrémités, ladite première extrémité étant adaptée pour être accouplée audit porte-outil;
des moyens accouplés à ladite seconde extrémité dudit arbre de broche rotatif (202) pour entraîner en rotation ledit arbre de broche rotatif (202), lesdits moyens d'entraînement en rotation comprenant un carter (216) qui part de ladite seconde extrémité et possède une ouverture traversante s'étendant le long dudit axe (218) depuis une extrémité dudit carter (216) jusqu'à l'autre extrémité;
une vis à rouleaux (222) comprenant une broche filetée (224) s'étendant le long dudit axe (218) et au moins un corps formant écrou (226,228) accouplé de façon opérationnelle à la broche, ladite vis à rouleaux (222) étant montée de manière que le mouvement de rotation de ladite broche filetée (224) autour dudit axe (218) provoque un déplacement dudit au moins un corps formant écrou (226,228) le long dudit axe (218);
des moyens comprenant un accouplement (254) accouplé entre ladite broche filetée (224) et l'arbre (256) du moteur (250) pour entraîner en rotation, d'une manière commandable, ladite broche filetée (224);
des moyens comprenant une barre de traction (220), qui est montée, d'une manière déplaçable en va-et-vient, dans ledit arbre de broche rotatif (202) et s'étend le long dudit axe (218), ladite barre de traction (220) étant adaptée pour être accouplée audit porte-outil de manière à tourner de concert avec ce dernier lorsque ledit porte-outil tourne, et peut provoquer un déplacement radial dudit outil de coupe lorsque ladite barre de traction (220) est déplacée en va-et-vient; et
des moyens positionnés dans ladite ouverture et accouplés à ladite barre de traction (220) et audit au moins un corps formant écrou (226,228) pour déplacer en va-et-vient ladite barre de traction (220) le long dudit axe (218) en réponse à un déplacement dudit au moins un corps formant écrou (226,228) le long dudit axe (218),
caractérisé en ce que la vis à rouleaux (222) comprenant la broche filetée (224) et le au moins un corps formant écrou (226,228) est montée dans ladite ouverture dudit carter (216), que ledit carter (216) est tourillonné, à l'aide de voies de roulements à billes (280,282) situées au moins aux extrémités du carter (216), de manière à tourner autour d'un manchon fixe (262) logeant la vis à rouleaux (222), et qu'un support fixe (270) pour le moteur (250) servant à faire tourner la broche filetée (224) pour actionner la barre de traction (220) est fixé au manchon fixe (262).

Ansprüche

1. Einstellbare Werkzeugantriebsanordnung eines Typs, der eine longitudinale Rotationsachse (6) umgibt und für die Ankopplung eines Werkzeughalters (8) geeignet ist, der um die genannte Achse (6) rotiert und mindestens ein Schneidwerkzeug (10, 12) enthält, welches bezüglich der genannten Achse (6) radial verstellbar ist, mit
   einem Spindelgehäuse (36) zur nicht-drehbaren Montage, welches innen einen Hohlraum aufweist, der längs der genannten Achse von einem ersten zu einem zweiten Ende reicht;
   einer Spindelwelle (34), die drehbar in dem genannten Spindelgehäuse angeordnet ist, sich durch den Hohlraum erstreckt, eine längs der Achse (6) vom einen Ende zum anderen verlaufende Ausnehmung aufweist und am einen Ende mit dem Werkzeughalter (8) koppelbar ist,
   wobei die drehbare Spindelwelle (34) durch eine Mehrzahl von Kugellaufbahnen (38) mindestens an den Enden der Welle (34) zur Drehung bezüglich des nichtdrehbaren Spindelgehäuses (36) gelagert ist,
   einer mit der drehbaren Spindelwelle (34) gekoppelten Vorrichtung zum Drehen der drehbaren Spindelwelle (34);
   einer Rollschraube (50), die eine sich längs der genannten Achse (6) erstreckende Leitschraubenspindel (52) und mindestens einen mit dieser funktionsmäßig gekoppelten Mutternkörper (54, 56) enthält und so angeordnet ist, daß eine Drehbewegung der Leitschraubenspindel (52) um die genannte Achse (6) eine Bewegung des mindestens einen Mutternkörpers (56, 54) längs der genannten Achse (6) bezüglich der Spindelwelle bewirkt,
   einer Vorrichtung, die eine zwischen die Leitschraubenspindel (52) und den Motor gekoppelte Antriebswelle (78) enthält, um die Leitschraubenspindel (52) kontrolliert zu drehen,
   einer Vorrichtung, die eine Zugstange (14) enthält, welche hin- und herbeweglich innerhalb der genannten Ausnehmung angeordnet ist, sich längs der genannten Achse (6) erstreckt und mit dem Werkzeughalter (8) gekoppelt ist, um sich mit diesem zu drehen, wenn der Werkzeughalter (8) gedreht wird, und um eine Radialbewegung des Schneidwerkzeuges (10, 12) zu bewirken, wenn die Zugstange (14) hin- und herbewegt wird; und
   einer in der Ausnehmung angeordneten Vorrichtung, die mit der Zugstange (14) und dem mindestens einen Mutternkörper (54, 56) gekoppelt ist, um die Zugstange (14) als Reaktion auf die längs der Achse (6) verlaufende Bewegung des mindestens einen Mutternkörpers (54, 56) längs der Achse (6) hin- und herzubewegen, wobei die hin- und hergehende Vorrichtung nicht drehbar ist,
dadurch gekennzeichnet, daß die Rollschraube (50) einschließlich der Leitschraubenspindel (52) und des mindestens einen Mutternkörpers (54, 56) in der genannten Ausnehmung der drehbaren Spindelwelle (34) montiert ist, daß ein Motorlagerungsgehäuse (102) auf einer stationären Motorhalterung (106) drehbar gelagert ist, wobei das Gehäuse (102) drehbar mit der drehbaren Spindelwelle (34) verbunden ist und daß der an der stationären Motorhalterung (106) montierte Motor (74) die Leitschraubenspindel (52) zur Betätigung der Zugstange (14) zu drehen gestattet.

2. Werkzeug nach Anspruch 1, dadurch gekennzeichnet, daß die hin- und hergehende Vorrichtung ein Gleitstück (58) enthält, das sich längs der genannten Achse (6) erstreckt und ein erstes offenes Ende (60) sowie ein axial beabstandetes zweites offenes Ende (62) aufweist, und daß das eine Ende der Zugstange (14) in das erste offene Ende (60) reicht und eine hiermit gekoppelte Anordnung enthält, um eine axiale Bewegung der Zugstange (14) bezüglich des Gleitstücks (58) zu verhindern, eine Drehung der Zugstange (14) bezüglich des Gleitstückes (58) jedoch zu gestatten.

3. Werkzeug nach Anspruch 2, dadurch gekennzeichnet, daß ein Teil (72) der Leitschraubenspindel (52) in das zweite offene Ende (62) des Gleitstückes (58) reicht und daß der mindestens eine Mutternkörper (54, 56) funktionsmäßig mit dem genannten Teil (72) gekoppelt und an dem Gleitstück (58) angebracht ist, um eine Bewegung des mindestens einen Mutternkörpers (54, 56) bezüglich des Gleitstückes (58) zu verhindern.

4. Werkzeug nach Anspruch 2, dadurch gekennzeichnet, daß die die Leitschraubenspindel (52) drehende Vorrichtung ein Motor (74) ist und außerdem eine Anordnung enthält, um einen Teil (76) der Leitschraubenspindel (52), der aus dem zweiten offenen Ende (62) des Gleitstückes (58) herausreicht, mit dem Motor (74) zu koppeln.

5. Werkzeug nach Anspruch 4, dadurch gekennzeichnet, daß die Kopplungsanordnung eine Antriebswelle (78) enthält, die sich in die Spindelwelle (34) erstreckt, mit einem Ende (80) mit dem Motor (74) und mit dem anderen Ende (90) mit der Leitschraubenspindel (52) gekoppelt ist.

6. Werkzeug nach Anspruch 5, dadurch gekennzeichnet, daß eine stationäre Hülse (94) in der Spindelwelle (34) angeordnet und mit dem Gleitstück (58) verkeilt ist und daß die Antriebswelle (78) sich mittels einer Ausnehmung (96), die vom einen Ende zum entgegengesetzten Ende der Hülse reicht, durch die Hülse (94) erstreckt.

7. Werkzeug nach Anspruch 4, dadurch gekennzeichnet, daß der Motor (74) ein Schrittmotor ist.

8. Werkzeug nach Anspruch 7, dadurch gekennzeichnet, daß der Motor (74) mit einem Steuermechanismus gekoppelt ist.

9. Werkzeug nach Anspruch 1 mit einem Werkzeughalter (8), der mit dem einen Ende der drehbaren Spindelwelle (34) sowie der Zugstange (14) gekoppelt ist und mit dem ein zum Schneiden eines Werkstücks während einer Drehung der drehbaren Spindelwelle (34) um die genannte Achse (6) dienendes Schneidwerkzeug (10, 12) gekoppelt ist, welches zu einer Bewegung in radialer Richtung bezüglich der genannten Achse (6) veranlaßt wird, so daß eine Schneidkante des Schneidwerkzeuges (10, 12) als Folge einer Nockenwirkung zwischen dem Schneidwerkzeug (10, 12) und der Zugstange (14) bei einer Hin- und Herbewegung der Zugstange längs der Achse (6) in Eingriff bzw. außer Eingriff mit einem Werkstück gebracht wird.

10. Werkzeug nach Anspruch 9, dadurch gekennzeichnet, daß die die Leitschraubenspindel (52) drehende Vorrichtung ein Motor (74) ist.

11. Werkzeug nach Anspruch 10, dadurch gekennzeichnet, daß der Motor (74) ein Schrittmotor ist.

12. Werkzeug nach Anspruch 8, dadurch gekennzeichnet, daß mit dem Steuermechanismus und dem Motor (74) ein Codierer gekoppelt ist.

13. Werkzeug nach Anspruch 11, dadurch gekennzeichnet, daß der Motor (74) mit einem Steuermechanismus gekoppelt ist.

14. Werkzeug nach Anspruch 13, dadurch gekennzeichnet, daß ein Codierer mit dem Steuermechanismus und dem Motor (74) gekoppelt ist.

15. Einstellbare Werkzeugantriebsanordnung (200) eines Typs, der eine longitudinale Drehachse (218) umgibt und zur Ankopplung eines Werkzeughalters geeignet ist, der um die genannte Achse (218) rotiert und mindestens ein Schneidwerkzeug enthält, das bezüglich der genannten Achse (218) radial verstellbar ist, mit
   einer Spindelwelle (202), die drehbar gelagert ist, eine Achse (218) sowie ein erstes und ein zweites Ende hat, von denen das erste Ende mit dem Werkzeughalter koppelbar ist;
   einer mit dem zweiten Ende der drehbaren Spindelwelle (202) gekoppelten Vorrichtung zum Drehen der drehbaren Spindelwelle (202), welche Drehvorrichtung ein Gehäuse (216) enthält, das sich vom zweiten Ende weg erstreckt und eine durchgehende Ausnehmung aufweist, die sich längs der genannten Achse (218) von einem Ende des Gehäuses (216) zum anderen erstreckt,
   einer Rollschraube, (222) mit einer sich längs der genannten Achse (2178) erstreckenden Leitschraubenspindel und mindestens einem mit dieser funktionsmäßig gekoppelten Mutternkörper (226, 228), wobei die Rollschraube (222) so angeordnet ist, daß eine Drehbewegung der Leitschraubenspindel (224) um die genannte Achse (218) eine Bewegung des mindestens einen Mutternkörper (226, 228) längs der genannten Achse (218) bewirkt;
   einer Vorrichtung, die eine Kupplung (254) enthält, die zwischen die Leitschraubenspindel (224) und die Motorwelle (256) des Motors (250) gekoppelt ist, um die Leitschraubenspindel (224) kontrolliert zu drehen,
   einer Vorrichtung, die eine Zugstange (220) enthält, die hin- und herbeweglich in der drehbaren Spindelwelle (202) angeordnet ist, sich längs der genannten Achse (218) erstreckt und mit dem Werkzeughalter koppelbar ist, um sich mit diesem zu drehen, wenn der Werkzeughalter gedreht wird, und um eine Radialbewegung des Schneidwerkzeugs zu bewirken, wenn die Zugstange (220) hin- und herbewegt wird, und
   einer in der Ausnehmung angeordneten und mit der Zugstange (220) sowie dem mindestens einen Mutternkörper (226, 228) gekoppelten Vorrichtung zum Hin- und Herbewegen der Zugstange (220) längs der Achse (218) als Reaktion auf eine Bewegung des mindestens einen Mutternkörpers (226, 228) längs der genannten Achse (218),
dadurch gekennzeichnet, daß die Rollschraube (222) einschließlich der Leitschraubenspindel (224) und des mindestens einen Mutternkörpers (226, 228) in der genannten Ausnehmung des Gehäuses (216) angeordnet ist; daß das Gehäuse (216) durch Kugellaufbahnen (280, 282) an mindestens einem Ende des Gehäuses (216) um eine stationäre Hülse (262) drehbar gelagert ist, welche die Rollschraube (222) aufnimmt, und daß eine stationäre Motorhalterung (270) für den Motor (250) zum Drehen der Leitschraubenspindel (224) zur Betätigung der Zugstange (220) an der stationären Hülse (262) befestigt ist.

Drawing